Don't override managed version of httpclient for LFS server tests

The version is 4.5.5 in the master pom.xml but overridden with 4.3.6
in the LFS server tests pom.xml.

Remove the override so that the same version is used everywhere.

Change-Id: Ibccc93a0c2a9c05db23cf131585184d67611b579
Signed-off-by: David Pursehouse <david.pursehouse@gmail.com>

org.eclipse.jgit.lfs.server.test/pom.xml

@@ -111,7 +111,6 @@
     <dependency>
       <groupId>org.apache.httpcomponents</groupId>
       <artifactId>httpclient</artifactId>
-      <version>4.3.6</version>
     </dependency>
   </dependencies>